With the development of communication technology and miniaturized electronic devices, personal terminals are being spread among general consumers. For example, personal computers and laptop computers are being widely spread. In particular, in recent years, personal handheld terminals such as a smartphone and a smart tablet have been widely spread.
In general, a personal terminal may be used by one user. Private information of a user may be stored in a personal terminal. Therefore, when a person other than the user accesses the terminal, privacy of the user may be invaded.
In order to prevent private information of a user from being accessed by a person, a terminal may be in a locked state while the user does not use the terminal. When the terminal is in a locked state, functions of the terminal may be restricted. When the terminal is in a locked state, a lock screen may be displayed.
When the terminal is in a locked state, the user may input a password that is registered in advance and thus release the locked state. When the user inputs a password, if a person near the user steals a password that the user inputs, the person may know the password. When the person releases a locked state of the terminal using the password, privacy of the user may be invaded.